Plant cryopreservation is a genetic resource conservation strategy that allows plant material, such as seeds, pollen, shoot tips or dormant buds to be stored indefinitely in liquid nitrogen. After thawing, these genetic resources can be regenerated into plants and used on the field. While this

cryopreservation Cryo-preservation or cryo-conservation is a process where Organism, organisms, organelles, cell (biology), cells, Biological tissue, tissues, extracellular matrix, Organ (anatomy), organs, or any other biological constructs susceptible to damage ...

conservation strategy can be used on all plants, it is often only used under certain circumstances: 1) crops with

recalcitrant Recalcitrant seeds are seeds that do not survive drying and freezing during ex-situ conservation. By and large, these seeds cannot resist the effects of drying or temperatures less than 10 °C (50 °F); thus, they cannot be stored for long periods ...

seeds e.g.

avocado The avocado (''Persea americana'') is a medium-sized, evergreen tree in the laurel family (Lauraceae). It is native to the Americas and was first domesticated by Mesoamerican tribes more than 5,000 years ago. Then as now it was prized for i ...

, coconut 2) seedless crops such as cultivated banana and plantains or 3) crops that are clonally propagated such as cassava, sweet potato.

History

The history of plant cryopreservation started in 1965 when Hirai was studying the biology activities that happened when biological samples were frozen. Three years later, there was the first successful attempt cryopreserving

callus A callus is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may o ...

cells. The following years, new methods to cryopreserve were developed, such as direct immersion, slow freezing and vitrification, as well as applied to more and more plants species and plant tissues.

Methods

* ''Direct immersion''. This is the immersion of plant material directly in liquid nitrogen, or after desiccation. This is often done with (orthodox) seeds that already have a low moisture content or pollen. This method cannot be used with tissues that contain a lot of water or are sensitive to dehydration. * ''Slow freezing''. This method relies on the mechanism of freeze dehydration to pull water out of the cells and thus prevent ice formation in the cell. * ''Vitrification.'' By freezing at an ultra-fast rate and using osmotic dehydration, the water that is still present in the cell is unable to form crystals and will be part of a glass-like or

vitrified Vitrification (from Latin ''vitreum'', "glass" via French ''vitrifier'') is the full or partial transformation of a substance into a glass, that is to say, a non-crystalline amorphous solid. Glasses differ from liquids structurally and glasses po ...

solution. This method can be further split in different variants e.g. droplet vitrification, encapsulation dehydration and plate vitrification.

Hurdles and limitations

Aside from the challenges involved with

in general, an important hurdle, when developing cryopreservation protocols for storage of plant germplasm, is that plants within a species can have a different tolerance to cryopreservation. This difference seems to be linked with the drought resistance of the different cultivars within the species. Even within the plant itself there can be noticeable differences depending on the tissue that is used, as both structure and composition play an important role during cryopreservation.

Organizations relying on plant cryopreservation

* Alliance of Bioversity International and Ciat *

International Potato Center The International Potato Center (known as CIP from its Spanish language, Spanish-language name ''Centro Internacional de la Papa'') is a research facility based in Lima, Peru, that seeks to reduce poverty and achieve food security on a sustaine ...

* Huntington Garden * Rural development administration of Korea *

Leibniz Institute of Plant Genetics and Crop Plant Research Gottfried Wilhelm (von) Leibniz . ( – 14 November 1716) was a German polymath active as a mathematician, philosopher, scientist and diplomat. He is one of the most prominent figures in both the history of philosophy and the history of mathema ...

References

{{reflist Cryopreservation Plant conservation